Retrofit assessment of masonry buildings through simplified structural analysis

The current seismic prevention strategy is based on a unitary approach aimed at a risk mitigation, also at territorial level. The Italian guidelines for the assessment and mitigation of seismic risk of cultural heritage provides indications for the seismic analysis of protected cultural heritage, with the aim of specifying a path of knowledge, assessing the level of safety and planning possible improvements. The Italian building heritage is very vast and heterogeneous and was devastated by earthquakes due to its high vulnerability; therefore, the seismic risk mitigation also requires the availability of simple and handy analysis tools. The aim of this paper is the illustration of an easy, although approximate, procedure for the evaluation of the seismic safety index and the optimization of strengthening interventions. The procedure is applied to buildings located in the province of Caserta. The analyses are performed with reference to two types of buildings that are particularly recurrent and representative of the building heritage of this area and placed in areas with different seismic hazard

Rocking Analysis for the bell tower of Sant’anna in Cervino

In seismic prone areas ecclesiastical masonry complexes have shown a very high vulnerability, as detected after the last Italian earthquakes, such as those occurred in L'Aquila (2009), Emilia-Romagna (2012), Central Italy (2016), and Ischia (2017). These are particular types of aggregate buildings subjected often to partial collapses, due to the presence of highly vulnerable elements, like the bell towers. Preliminary analyses should including straightforward and quick methods are necessary. In this paper the bell tower vulnerability is analyzed taking into account the rocking behaviour of the tower only and considering the contribute of the entire ecclesiastical complex as a rigid body sliding with a fixed friction coefficient with respect to the foundations. It is shown that suitable values of maximum oscillations and horizontal displacements are obtained. The case study is the ecclesiastical complex of S. Anna in Cervino (Caserta, Italy)

Diagnostic reliability in the assessment of degradation in precast concrete elements

In the past century, precast reinforced concrete has become the most widely used construction material in infrastructure engineering, especially for long-span structures. Nowadays, a growing research area concerns the assessment of concrete strength degradation due to environmental exposure and reinforcement corrosion. This paper reports an experimental campaign on some prefabricated concrete elements that were exposed to atmospheric agents for approximately 20 years. The campaign took the uncommon opportunity to access the full inspection and sampling of rebar. The included activities had different invasiveness and encompassed inspections, core sampling, corrosion potential mapping, compressive strength tests, as well as neutralization depth assays on cored surfaces, on chisel-split surfaces, and on drilling powders. The results bring together a global diagnostic picture of very limited degradation and of elements that are fully able to attend their design service life; the latter is estimated to be considerably higher than 20 years and to exceed 75 years if the concrete mix does not show quality issues. Results also permit drawing considerations on a hierarchy of diagnostic reliability in the evaluation of RC degradation, in which concrete core sampling plays the role of golden standard

Seismic safety of simple masonry buildings

Italian and European seismic codes differ in requirements for simple masonry buildings. The paper is aimed at evaluating the seismic response of unreinforced masonry buildings complying with the provisions of the Italian national code. Indications are supplied on the congruence between code rules and results of nonlinear static analyses performed according to the code itself. The results provide a contribution for improving the seismic code requirements

Out of plane behaviour of unreinforced masonry walls

The behaviour of unreinforced masonry walls has been widely investigated in order to assess the seismic vulnerability of masonry structures. Even if partial analyses are not sufficient for a full structural analysis under seismic actions, they can be used to have quick estimation of both collapse load and failure mechanisms. Simplified out-of-plane collapse mechanisms, taking into account connections with floor and transversal walls, are considered to evaluate the behaviour of masonry walls subjected to out of plane forces. In general cantilever walls and walls supported only at the top and bottom edges can be represented as equivalent SDOF system, in order to evaluate by simple static analysis the limit horizontal force at the threshold of rocking, assuming that the wall has cracked and hence the tensile strength of the mortar can be neglected. Similarly, the displacement at the threshold of overturning can be obtained from that simple kinematic model. The value of the collapse load and the consequent load-displacement behaviour is strongly related to the way of computing the displacements and to the way of cracking. This paper presents some remarks on the evaluation of the effective secant stiffness of an unreinforced masonry wall in out of plane loading. Comparisons with the Priestley model are shown

The role of friction in the seismic risk mitigation of freestanding art objects

The problem of reducing the seismic risk for art objects, that are the objects generally contained within Museums, is of great interest. The first studies were performed in Japan and were successively organized in a general framework by a research program performed at Southern California University and sponsored by the Getty Museum at Malibu, California. In these papers and in the following Italian studies, the theoretical models for the problem concerning to vases and statues are based on the dynamic behaviour of rigid blocks and have been deeply developed. Unfortunately, because of the great lack of experimental data, determinant parameters for the problem characterization (like the friction between two superimposed blocks or between the art object and the support plane) are often assumed without reference to real values derived from laboratory tests. This paper presents the results of a research program containing the experimental determination of the friction coefficient between the art object and the support (by means of a testing apparatus ad hoc on purpose realized) together with dynamic tests performed on simple shaped objects made of different materials. The dynamic tests were performed using an unidirectional shaking table and different supporting surfaces, so that the influence of different friction coefficients has been analyzed